Formation of an emulsion in a fluid microsystem

Abstract

There is described a method for forming an emulsion ( 1 ) containing at least one dispersed phase ( 3 ) and a continuous phase ( 2 ) in a fluidic microsystem ( 100 ), said method comprising the steps: forming flows ( 4, 5 ) of different liquids which flow towards a dispersion region ( 10 ), and forming the emulsion ( 1 ) from the liquids in the dispersion region ( 10 ), wherein the flows ( 4, 5 ) run through a common channel ( 20 ) to the dispersion region ( 10 ) and the flows ( 4, 5 ) are arranged next to one another relative to a first reference direction, and wherein the emulsion ( 1 ) is produced as the liquids flow through a cross-sectional widening ( 11 ) provided in the dispersion region ( 10 ), at which the cross section of the channel ( 20 ) widens in a second reference direction different from the first reference direction. A fluidic microsystem for forming an emulsion ( 1 ) containing a continuous phase ( 2 ) and at least one dispersed phase ( 3 ) is also described. A fusion of droplets in electric fields is also described.

1. A method for forming an emulsion including at least one dispersed phase and a continuous phase in a fluidic microsystem, said method comprising the following steps:
 forming flows of different liquids which flow towards a dispersion region, and 
 forming the emulsion from the liquids in the dispersion region, 
 wherein 
 the flows run through a common channel to the dispersion region, wherein the flows are arranged next to one another relative to a first reference direction, and 
 the emulsion is produced as the liquids flow through a cross-sectional widening provided in the dispersion region, at which the cross section of the channel widens in a second reference direction parallel to the channel height. 
 
     
     
       2. The method according to  claim 1 , in which the emulsion is produced as the liquids flow over a step provided in the dispersion region. 
     
     
       3. The method according to  claim 2 , in which at least one of the flows is fed into the channel through at least one injection channel. 
     
     
       4. The method according to  claim 3 , in which a plurality of flows is fed into the channel at a plurality of injection channels. 
     
     
       5. The method according to  claim 1 , in which the at least one dispersed phase comprises droplets, the diameter of which is less than 1000 μm. 
     
     
       6. The method according to  claim 5 , in which the at least one dispersed phase comprises droplets, the diameter of which is less than 200 μm. 
     
     
       7. The method according to  claim 1 , further comprising the following step:
 setting a predefined flow rate ratio which is a quotient of a flow rate of the flow for the dispersed phase and of a flow rate of the flow for the continuous phase. 
 
     
     
       8. The method according to  claim 7 , in which the flow rate ratio is set in the range from 0.1 to 0.9. 
     
     
       9. The method according to  claim 8 , in which the flow rate ratio is set in the range from 0.5 to 0.9. 
     
     
       10. The method according to  claim 1 , further comprising the following step:
 varying a chemical composition of at least one of the liquids. 
 
     
     
       11. The method according to  claim 10 , in which the at least one dispersed phase is formed as a succession of droplets, a chemical composition of which varies. 
     
     
       12. The method according to  claim 10 , in which the at least one dispersed phase is formed as a succession of droplets, each of which has a different pH value. 
     
     
       13. The method according to  claim 1 , in which the emulsion contains a plurality of dispersed phases, each of which comprises a succession of dispersed droplets. 
     
     
       14. The method according to  claim 1 , further comprising the following step:
 splitting the emulsion into at least two sub-emulsions. 
 
     
     
       15. The method according to  claim 14 , in which the sub-emulsions after splitting comprise droplets having a volume that is equal to a volume of the droplets of the emulsion. 
     
     
       16. The method according to  claim 14 , in which the sub-emulsions after splitting comprise droplets having a volume that is smaller than a volume of the droplets of the emulsion. 
     
     
       17. The method according to  claim 14 , in which the splitting of the emulsion takes place in multiple stages at a plurality of branchings. 
     
     
       18. The method according to  claim 14 , further comprising the following step:
 combining the sub-emulsions to form a common emulsion flow. 
 
     
     
       19. The method according to  claim 1 , comprising the step:
 rearranging the emulsion from a state in which the dispersed phase forms a simple succession of droplets to a state in which the dispersed phase forms a plurality of successions of droplets which are offset relative to one another. 
 
     
     
       20. The method according to  claim 1 , further comprising the following step:
 fusing two adjacent droplets of the at least one dispersed phase. 
 
     
     
       21. The method according to  claim 20 , in which the fusion takes place under the effect of an electric field, irradiation with light or local heating. 
     
     
       22. The method according to  claim 1 , further comprising the following step:
 synchronizing the formation of droplets of the at least one dispersed phase as a function of at least one time schedule. 
 
     
     
       23. The method according to  claim 22 , in which the synchronizing comprises a time control of the formation of droplets of a plurality of dispersed phases relative to one another. 
     
     
       24. The method according to  claim 22 , in which the synchronizing comprises a temporally controlled heating of the flows upstream of the dispersion region. 
     
     
       25. A fluidic microsystem for forming an emulsion including a continuous phase and at least one dispersed phase, said fluidic microsystem comprising:
 a dispersion region for forming the emulsion from different liquids, and 
 a channel which leads to the dispersion region, 
 wherein 
 the channel is designed in such a way that flows of the liquids in the channel run next to one another relative to a first reference direction, and 
 the channel has in the dispersion region a cross-sectional widening at which a cross section of the channel widens in a second reference direction parallel to the channel height. 
 
     
     
       26. The microsystem according to  claim 25 , in which the cross-sectional widening comprises a step. 
     
     
       27. The microsystem according to  claim 25 , in which the channel has an aspect ratio (W 1 /H 1 ), calculated from a width (W 1 ) parallel to the first reference direction and a height (H 1 ) perpendicular to the first reference direction, which is selected in a range from 100:1 to 2:1. 
     
     
       28. The microsystem according to  claim 25 , in which at least one injection channel is connected to the channel, through which injection channel at least one of the flows can be fed into the channel. 
     
     
       29. The microsystem according to  claim 28 , in which the channel is connected to a plurality of injection channels, at which a plurality of flows can be fed into the channel. 
     
     
       30. The microsystem according to  claim 25 , which has a dosing device for setting a predefined flow rate ratio of the flows. 
     
     
       31. The microsystem according to  claim 25 , which has an adjusting device for varying a chemical composition of at least one of the liquids. 
     
     
       32. The microsystem according to  claim 25 , which has a splitter device with at least one branching for splitting the emulsion into at least two sub-emulsions. 
     
     
       33. The microsystem according to  claim 32 , in which the splitter device has a plurality of branchings for splitting the emulsion in multiple stages. 
     
     
       34. The microsystem according to  claim 32 , which has a joining device for combining the sub-emulsions to form a common emulsion flow. 
     
     
       35. The microsystem according to  claim 25 , which has at least one fusion device for fusing two adjacent droplets of the at least one dispersed phase. 
     
     
       36. The microsystem according to  claim 35 , in which the fusion device comprises electrodes for generating an electric field, a light source or a heating device. 
     
     
       37. The microsystem according to  claim 25 , which has at least one synchronization device for synchronizing a formation of droplets of the at least one dispersed phase as a function of at least one time schedule. 
     
     
       38. The microsystem according to  claim 37 , in which the synchronization device has a heating device which is arranged in the channel. 
     
     
       39. A method for processing an emulsion containing droplets of a dispersed phase in a continuous phase in a fluidic microsystem according to  claim 25 , said method comprising the following steps:
 passing two droplets, which are to be made to interact, across electrodes which are arranged on at least one wall surface of a channel of the fluidic microsystem, 
 subjecting the electrodes to a voltage pulse, and 
 fusing the droplets. 
 
     
     
       40. The method according to  claim 39 , in which the electrodes are subjected to the voltage pulse when in each case one of the droplets is in contact with one of the electrodes. 
     
     
       41. The method according to  claim 39 , further comprising the following step:
 selecting parameters for controlling the electrodes as a function of a size of the droplets. 
 
     
     
       42. The method according to  claim 39 , in which the electrodes are subjected to a voltage pulse having an amplitude of less than 15 V. 
     
     
       43. The method according to  claim 39 , in which the electrodes are subjected to a voltage pulse having a duration of less than 100 ms. 
     
     
       44. A fusion device for fusing droplets of a dispersed phase in a continuous phase in a channel of a fluidic microsystem according to  claim 25 , said fusion device comprising:
 at least two electrodes which are arranged on at least one wall surface of a channel of the fluidic microsystem, and 
 a control circuit which is designed to subject the electrodes to a voltage pulse when the droplets move past the electrodes so as to fuse the droplets of the dispersed phase in the continuous phase. 
 
     
     
       45. The fusion device according to  claim 44 , in which the control circuit is designed to subject the electrodes to a voltage pulse having an amplitude of less than 15 V. 
     
     
       46. The fusion device according to  claim 44 , in which the control circuit is designed to subject the electrodes to a voltage pulse having a duration of less than 100 ms. 
     
     
       47. The fusion device according to  claim 44 , in which the electrodes are arranged in such a way that an electric field can be produced with a direction differing from a longitudinal extension of the channel. 
     
     
       48. The fusion device according to  claim 47 , in which the electrodes are arranged in such a way that an electric field can be produced with a direction oriented transversely to the longitudinal extension of the channel. 
     
     
       49. The fusion device according to  claim 47 , in which the electrodes are arranged on the at least one wall surface of the channel in such a way that they protrude from two sides towards a center of the channel. 
     
     
       50. The fusion device according to  claim 44 , in which the electrodes are arranged in such a way that an electric field can be produced with a direction which runs parallel to a longitudinal extension of the channel. 
     
     
       51. The fusion device according to  claim 44 , in which the electrodes comprise electrically conductive layers on the at least one wall surface of the channel. 
     
     
       52. The fusion device according to  claim 44 , in which the at least two electrodes comprise one or more electrode arrays in each case with a plurality of electrodes which are arranged on at least one of a bottom, top and side surfaces of the channel.